THIS invention relates to a spectroscopic analyzing arrangement which incorporates an optical device for multi-bounce attenuated total reflection (ATR) spectroscopic analysis.
According to the invention there is provided a spectroscopic analyzing arrangement comprising an ATR optical sampling plate having a front sample-contacting face,and an opposed rear internally reflecting face, an anvil assembly located rearwardly of the rear reflecting face for allowing the sample-contacting face to be pressed sufficiently hard against the sample to receive spectroscopic information therefrom, and a reflection barrier located between the anvil assembly and the rear internally reflecting face of the sampling plate for preventing internally reflected light within the sampling plate from picking up spectroscopic information from the anvil assembly.
In a preferred form of the invention, the anvil assembly comprises an anvil and a prism having an entry facet for receiving incident light and an exit facet for allowing light reflected within the sampling plate to exit, the prism having a front face arranged to make contact with the rear reflecting face of the sampling plate via the reflection barrier and an opposed rear face against which the anvil locates.
Conveniently, an outer peripheral support is fixed to the outer periphery of the sampling plate, preferably by gluing or brazing, with entry and exit passages being defined in the outer peripheral support for receiving the incident and reflected light beams.
Both the sampling plate and the prism are typically formed from a diamond material such as a type IIA or a CVD diamond.
The reflection barrier is conveniently in the form of a reflective metallic coating having a maximum thickness of 10% of the wavelength of light used.
The coating is preferably coated onto the front face of the prism but may also be applied directly to the rear internally reflecting face of the sampling plate, if it allows good internal reflection from its adhesion layer.